/*
 * Copyright 1999-2018 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.alibaba.nacos.core.notify;

import java.io.Serializable;

/**
 * @author <a href="mailto:liaochuntao@live.com">liaochuntao</a>
 */
public interface Event extends Serializable {

    /**
     * Event sequence number, which can be used to handle the sequence of events
     *
     * @return sequence num, It's best to make sure it's monotone
     */
    default long sequence() {
        return System.currentTimeMillis();
    }

}
